1. Field of the Invention
The present invention relates to a field winding type rotary electric machine chiefly incorporated into a vehicle and provided with a control apparatus as well as having an armature winding and a field winding.
2. Background Art
A rotary electric machine for vehicle is generally incorporated into an engine room. An operating temperature of the rotary electric machine for vehicle is therefore extremely high. An internal temperature of the rotary electric machine for vehicle rises further due to heat generated by the rotary electric machine for vehicle in association with power generating and driving operations. Hence, when a temperature of the rotary electric machine for vehicle rises exceedingly due to a continuous operation over a long period, the rotary electric machine for vehicle may possibly break down because of damage on inner parts.
To overcome this inconvenience, an output control method and an output control apparatus of an AC generator for vehicle in the related art propose a technique as follows as a prevention of a breakdown of the AC generator for vehicle caused by a rise in temperature. That is, a temperature of the AC generator or ambient temperature thereof is measured and an output current of the AC generator is limited upon detection of the measured temperature exceeding a pre-set abnormal temperature value so that thermal burden on the control apparatus is lessened (see, for example, Patent Document 1).
The output control method and the output control apparatus described in Patent Document 1, however, protect the AC generator for vehicle against a rise in temperature by limiting a field current according to the temperature of the AC generator for vehicle detected by a temperature sensor. Accordingly, there is a need to incorporate the temperature sensor and this need poses a problem that the cost of the AC generator for vehicle increases and the structure thereof has to be changed.
To eliminate this problem, Patent Document 2 describes a technique to prevent an excessive rise in temperature by limiting a field current to be passed to a range within which no damage is caused by heat generation in a case where a field current flowing to a field winding remains at or above a predetermined threshold value for a predetermined time.
Patent Document 1: JP-A-8-9567 (FIG. 1 and a description thereof)
Patent Document 2: JP-A-2010-279085 (FIG. 3 and a description thereof)
The AC generator for vehicle described in Patent Document 2, however, is silent about a case where an initial temperature condition of the AC generator for vehicle is unknown, such as at the start-up of the power supply. For example, in a case where the internal temperature of the AC generator for vehicle is high at the start-up of the power supply, it is difficult to prevent a rise in temperature at appropriate timing with the technique in the related art in which no temperature sensor is incorporated. Hence, in such a case, an excessive rise in temperature may possibly give rise to damage on the AC generator for vehicle.